1. Field of the Invention
The invention relates to a thermally-assisted magnetic recording head that uses lowering in coercivity caused by irradiation of near-field light to record information in a magnetic recording medium, and to a head gimbals assembly, a head arm assembly, and a magnetic recording unit that are each provided with the thermally-assisted magnetic recording head.
2. Description of Related Art
In the past, a magnetic recording unit such as a hard disk drive (HDD) has been used for magnetically writing and reading information.
The magnetic disk unit typically includes a magnetic recording medium (a magnetic disk) and a magnetic read write head that performs a write process and a read process of information. The magnetic read write head is formed on one surface of a magnetic head slider, and has a surface (an air-bearing surface) facing the magnetic disk. The magnetic head slider is provided on one end of a suspension, and the other end of the suspension is attached to a pivotable arm.
In recent years, along with a progress in higher recording density (higher capacity) of the magnetic disk, improvement in performance of the magnetic read write head has been demanded. Therefore, as a magnetic recording system capable of dealing with higher recording density, a thermally-assisted magnetic recording system has been studied. In the thermally-assisted magnetic recording system, a magnetic disk in which a magnetic recording layer has large coercivity is used, and heat is applied to a recording region (a region where information is to be recorded) of the magnetic recording layer together with a recording-use magnetic field (recording magnetic field) at the time of writing. Accordingly, the coercivity of the recording region is lowered as well as the recording region is magnetized in response to temperature increase, and therefore information is written.
In the thermally-assisted magnetic recording system, near-field light is generally used for supplying heat to a magnetic disk. Accordingly, a magnetic recording head of the thermally-assisted magnetic recording system (a thermally-assisted magnetic recording head) includes a light source generating laser light, a waveguide allowing the laser light to propagate therethrough, a plasmon generator generating the near-field light, and a magnetic pole generating recording magnetic field. The plasmon generator is disposed between the waveguide and the magnetic pole. When surface plasmons are generated by the plasmon generator, the surface plasmons are used to generate the near-field light in the vicinity of the air-bearing surface in the thermally-assisted magnetic recording head, and thus heat is supplied to the magnetic disk.
In the case where the near-field light is used, in Japanese Patent No. 4104584 specification, surface plasmon polariton coupling is used in order to prevent overheat of the plasmon generator due to direct irradiation of light. In this case, the light propagating through the waveguide (guided light) is not directly applied to the plasmon generator, and the guided light is coupled to the plasmon generator through evanescent coupling. As a result, surface plasmon polaritons are generated on a surface of the plasmon generator.
In the case of using the surface plasmon polaritons, in U.S. Pat. No. 8,400,885 specification, a spot diameter of the near-field light is made small and the shape of a tip surface of the plasmon generator is formed into a rectangle in order to make the gradient of light intensity steep. In this case, since light is collected to the vicinity of the tip surface of the plasmon generator, intensity of the light is increased.
When light absorption amount of the plasmon generator is increased in response to increase in the light intensity, the plasmon generator generates heat (is thermally expanded), and thus easily protrudes toward the magnetic recording medium. In this case, a distance between the plasmon generator and the magnetic recording medium is shorter than an appropriate value, which may cause unintentional collision between the plasmon generator and the magnetic recording medium. If the plasmon generator and the magnetic recording medium collide with each other, the plasmon generator is deformed or broken, which results in degradation in generating capacity of the near-field light. Accordingly, recording property is degraded.
Therefore, is it desirable to provide a technology capable of obtaining excellent recording performance.